Regeneration method with efficient oxygen utilization

ABSTRACT

This invention relates to regeneration of coked catalyst by combustion so that the catalyst can be reused in a hydrocarbon conversion reaction. The completion of coke burn is generally measured with a combination of temperature or change in oxygen concentration. Dropping outlet temperatures require time to wait for increases in inlet temperature to correspondingly move down the regenerator. Faster response times might be expected from increasing oxygen concentration, but a small increase in concentration can lead to a significant increase in peak burn temperature which negatively impacts catalyst life. Controlled peak burning is difficult over the entire bed by merely controlling inlet and outlet oxygen concentrations. The invention accordingly combines a measured lag time for temperature travel with an inlet temperature ramping step to ensure complete coke combustion with high oxygen efficiency, thus providing a rapid regeneration that permits more time for operation at desired reaction conditions.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Division of copending application Ser. No.10/750,292 filed Dec. 31, 2003, the contents of which are herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to the art of catalytic conversion ofhydrocarbons to useful hydrocarbon products. More specifically, itrelates to the reconditioning of spent hydrocarbon conversion catalystso that the catalyst can be reused in a hydrocarbon conversion reaction.

BACKGROUND OF THE INVENTION

Catalytic processes for the conversion of hydrocarbons are well knownand extensively used. Invariably the catalysts used in these processesbecome deactivated for one or more reasons. Where the accumulation ofcoke deposits causes the deactivation, reconditioning of the catalyst toremove coke deposits restores the activity of the catalyst. Coke isnormally removed from catalyst by contact of the coke-containingcatalyst at high temperature with an oxygen-containing gas to combustand to remove the coke in a regeneration process. These processes can becarried out in-situ within a fixed-bed or the catalyst may be removedfrom a vessel in which the hydrocarbon conversion takes place andtransported to a separate regeneration zone for coke removal.Arrangements for continuously or semi-continuously removing catalystparticles from a reaction zone and for coke removal in a regenerationzone are well known.

In a continuous or semi-continuous regeneration process, coke ladenparticles are at least periodically added and withdrawn from a bed ofcatalyst in which the coke is combusted. In those processes having anessentially linear progression of catalyst particles through the bed anda transverse flow of oxidizing gas coke combustion, there are regions ofintense burning that extend through portions of the catalyst bed.

In a fixed-bed or batch process, coke laden particles are likewisesubjected to a flow of oxidizing gas, but the gas is flowed axiallythrough the bed instead of the particles being flowed through the gas.Similarly, there is a region of intense burning as gas travels down thebed with rising temperature as oxygen in the gas is consumed.

These regions of intense burning are important for complete cokeremoval, but are also difficult to control in a time efficient manner.Typically coke removal takes a significant amount of time to complete.Any extra time used to ensure complete combustion leads to productionlosses in an existing regenerator unit with less available reconditionedcatalyst, which would otherwise be used for valuable hydrocarbonconversion reactions. Investment losses also occur for oversizedequipment built at a larger size than necessary for a new regeneratorunit.

For a fixed-bed regeneration process, the completion of coke burn isgenerally measured with a combination of bed temperature or change inoxygen concentration. Once satisfactory burn criteria have been met, aproof burn is conducted by increasing the regenerator temperature or theoxygen concentration. However, the measurement of the parameters outsidethe regenerator to set criteria for end of burn require scrutiny inorder to avoid regenerator outlet temperature dropping below the peakburn temperature or outlet oxygen concentration increasing, whichreflects dropping oxygen utilization. Dropping outlet temperaturesrequire additional lag time to wait for increases in inlet temperatureto correspondingly move down the regenerator.

Faster response times can be expected from increasing oxygenconcentration, but a small increase in concentration can lead to asignificant increase in peak burn temperature. Some beds have low flowareas where oxygen in the effluent can increase, while the low flow areacontinues to consume all of the available oxygen, thus making controlledpeak burning difficult over the entire bed by merely controlling inletand outlet oxygen concentrations.

Another problem associated with localized regions of intense cokecombustion is catalyst deactivation. Exposure of high surface areacatalyst to high temperatures for prolonged periods of time will createa more amorphous material having a reduced surface area which in turnlowers the activity of the catalyst until it reaches a level where it isconsidered deactivated. Deactivation of this type is permanent, therebyrendering the catalyst unusable. When moisture is present—water is aby-product of the coke combustion—the deactivating effects of hightemperature exposure are compounded.

The combination of temperature, water vapor, and exposure time determineuseful life of the catalyst. The burning of coke in localized portionsof a catalyst bed has the deleterious effect of heating gases andgenerating moisture that pass through downstream portions of the bed andextend the high temperature exposure time of catalyst particles in thebed.

U.S. Pat. No. 3,753,926 discloses a method for regenerating ahydrocarbon conversion catalyst comprising rhenium using two carbonburning steps, where the first step is at a relatively low temperaturewith a small amount of oxygen and the second step is at a relativelyhigher temperature and a relatively higher amount of oxygen.

U.S. Pat. No. 4,507,397 discloses a sulfur removal step in asemi-continuous regeneration process prior to carbonaceous depositoxidation. U.S. Pat. No. 4,810,683 discloses a method for regenerating aplatinum containing zeolite. U.S. Pat. No. 5,155,075 discloses a lowtemperature method for regeneration of a platinum containing zeolitethat uses a halogen-free oxygen gas.

U.S. Pat. No. 4,859,643 discloses a method for regeneratingcoke-contaminated catalyst particles that confines particles in thecombustion section of a regenerator zone to a tapered bed configuration,which achieves better utilization of oxygen and minimizes surface arealoss of the catalyst. This patent ('643) is hereby incorporated byreference into this patent application.

U.S. Pat. No. 5,001,095 discloses a method for improving a cokecombustion process by segregating flue gas from the process into a highmoisture content portion that is removed and a low moisture contentportion that is recycled to the process.

U.S. Pat. No. 5,151,392 discloses a moving bed regeneration process withseparate dispersion and chloriding steps following a coke combustionzone, which allows improved platinum re-dispersion by controllingchloride equilibrium with either oxygen-enriched or oxygen-depletedenvironments.

U.S. Pat. No. 5,854,162 discloses an offsite regeneration process usinga moving bed furnace for a combustion step similar for usedhydro-treatment catalysts, and adds a oxy-halogenation step in a sealedrotating furnace that avoids the onset of gas channeling, which improvesthe homogeneity of catalyst halogenation.

U.S. Pat. No. 5,965,473 discloses a method for reducing chlorideemissions from a cyclic regeneration operation while saving operatingcosts.

U.S. Pat. No. 6,103,652 discloses a staged combustion process andapparatus for regenerating a catalyst in a moving bed that includes atleast two separate successive combustion zones.

SUMMARY OF THE INVENTION

Ways are always sought to improve the effectiveness and economics ofregeneration systems, such that catalyst regeneration time is minimizedwhile catalyst reaction time is maximized. Accordingly, one embodimentof the present invention is a method for achieving increased burningefficiency of catalyst coke deposits by determining a lag time to usewith increasing inlet temperatures during a temperature ramping stepoccurring as coke combusts in a catalyst bed.

In another embodiment of the present invention, a ramp rate isiteratively determined by allowing the first cycle to occur withoutramping, then using the empirical information to set a time based onwhen the previous cycle coke burn completes.

In yet another embodiment of the present invention, an apparatus systemuses a heater and at least two vessels for reaction and regeneration toconduct coke combustion from catalyst particles. A measurement device isused in conjunction with a control device to permit a lag time tocompensate for temperature ramping in a beneficial manner.

Additional objects, embodiments and details of this invention can beobtained from the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows typical heat transfer profiles traveling axially through acatalyst bed at one minute intervals for bed heat-up prior tocombustion.

FIG. 2 shows inlet and outlet temperatures for a bed during combustionwhere temperature is ramped at about 83 minutes.

FIG. 3 shows axial bed profiles during combustion where temperature isramped at about 83 minutes.

FIG. 4 shows inlet and outlet temperatures for a bed during combustionwhere temperature is ramped at about 89 minutes.

FIG. 5 shows axial bed profiles during combustion where temperature isramped at about 89 minutes.

FIG. 6 shows a general schematic of the apparatus of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is applicable to a number of hydrocarbonconversion processes which utilize a catalyst and are generally depictedby FIG. 6. For example, it is useful in the isomerization of normalbutane to isobutane and the isomerization of mixed C₈ aromatics,including those of high ethylbenzene content, to meta-xylene orpara-xylene. The present invention may also be used in upgrading lightstraight run naphtha, which is a mixture rich in C₅ and C₆ paraffins(pentanes and hexanes), to the corresponding branched isomers, whichhave higher octane numbers than the feed naphtha. Another hydrocarbonconversion process in which the present invention may be used isdehydrogenation of light paraffins (C₂ to C₅, but primarily C₃ and C₄)to the corresponding olefins.

However, the most widely practiced hydrocarbon conversion process towhich the present invention is applicable is catalytic reforming.Therefore the discussion of the invention contained herein will be inreference to its application to a catalytic reforming reaction system.It is not intended that such discussion limit the scope of the inventionas set forth in the claims.

Catalytic reforming is a well-established hydrocarbon conversion processemployed in the petroleum refining industry for improving the octanequality of hydrocarbon feedstocks, the primary product of reformingbeing motor gasoline. The art of catalytic reforming is well known anddoes not require extensive description herein.

Briefly, in catalytic reforming, a feedstock (2) is admixed with arecycle stream comprising hydrogen and contacted with catalyst in areaction zone (4). The usual feedstock for catalytic reforming is apetroleum fraction known as naphtha and having an initial boiling pointof about 82° C. (180° F.) and an end boiling point of about 204° C.(400° F.). The catalytic reforming process is particularly applicable tothe treatment of straight run gasolines comprised of relatively largeconcentrations of naphthenic and substantially straight chain paraffinichydrocarbons, which are subject to aromatization through dehydrogenationand/or cyclization reactions.

Reforming may be defined as the total effect produced by dehydrogenationof cyclohexanes and dehydroisomerization of alkylcyclopentanes to yieldaromatics, dehydrogenation of paraffins to yield olefins,dehydrocyclization of paraffins and olefins to yield aromatics,isomerization of n-paraffins, isomerization of alkylcycloparaffins toyield cyclohexanes, isomerization of substituted aromatics, andhydrocracking of paraffins. Further information on reforming processesmay be found in, for example, U.S. Pat. No. 4,119,526; U.S. Pat. No.4,409,095; and U.S. Pat. No. 4,440,626.

A catalytic reforming reaction is normally effected in the presence ofcatalyst particles comprised of one or more Group VIII noble metals(e.g., platinum, iridium, rhodium, palladium) and a halogen combinedwith a porous carrier, such as a refractory inorganic oxide. Alumina isa commonly used carrier. The halogen is normally chlorine. The particlesare usually spheroidal but may be cylindrical, and have a diameter offrom about 1.5 mm to about 3.1 mm ( 1/16-inch to about ⅛-inch), thoughthey may be as large as 6.55 mm (¼-inch). In a particular regenerator,however, it is desirable to use catalyst particles which fall in arelatively narrow size range. During the course of a reforming reaction,catalyst particles become deactivated as a result of mechanisms such asthe deposition of coke on the particles; that is, after a period of timein use, the ability of catalyst particles to promote reforming reactionsdecreases to the point that the catalyst is no longer useful. Thecatalyst must be reconditioned, or regenerated, before it can be reusedin a reforming process.

The present invention is applicable to a moving bed regeneration zoneand a fixed bed regeneration zone. Fresh catalyst particles (6) areplaced in a reaction zone (4), which may be comprised of severalsubzones. Catalyst may be withdrawn from the bottom of the reaction zoneand transported (10) to a regeneration zone (12) where a hereinafterdescribed multi-step or multi-section regeneration process is used torecondition the catalyst to restore its full reaction promoting ability.Catalyst flows by gravity through the regeneration zone, and then iswithdrawn (6) and furnished to the reaction zone (4) Catalyst may flowthrough successive steps or sections, or successive steps may be appliedto a non-flowing section of catalyst. Similarly, a fixed bed or batchreaction zone may be switched into a regenerator zone by applyingsuccessive steps to a non-moving catalyst bed.

When using the method of this invention in a batch, continuous, orsemi-continuous catalyst regeneration process, catalyst is contactedwith a hot oxygen-containing gas stream (14) (known in reformingprocesses as recycle gas) in order to remove coke which accumulates onsurfaces of the catalyst while it is in a hydrocarbon conversionreaction zone. Coke is comprised primarily of carbon but is alsocomprised of a relatively small quantity of hydrogen. The mechanism ofcoke removal is oxidation mainly to carbon dioxide and water. Cokecontent of spent catalyst may be as much as 20% of the catalyst weight,but 5 to 7% is a more typical amount. Within the combustion step orsection, coke is usually oxidized at temperatures ranging from about371° to about 550° C. (700° to 1020° F.), but temperatures in localizedregions may reach as low as 200° C. (392° F.) and as high as 600° C.(1112° F.) or more. It is preferred to not greatly exceed 600° C. (1112°F.).

Oxygen (16) for the combustion of coke enters the combustion step of theregeneration zone in what has been termed a recycle gas. The recycle gascontains a low concentration of oxygen usually on the order of 0.2 to3.0% by volume. The arrangement of a typical combustion section for acontinuous regeneration zone may be seen in U.S. Pat. No. 3,652,231. Thearrangement for a batch regenerator zone may be seen by description inU.S. Pat. No. 5,965,473 which describes an off-stream catalyst bed of areforming process with cyclic catalyst regeneration. Such a batchregenerator zone contains catalyst particles in an elongated bed havingtwo elongated sides. In one common arrangement, the two elongated sidesare open for transverse gas flow through the catalyst bed. In anothercommon arrangement, the elongated bed has two ends, which are generallyperpendicular to the elongated sides and which are open for axial gasflow through the bed. If the arrangement is a cylinder, then it willonly have one elongated side.

As the coke is combusted, the small amount of hydrogen within the cokereacts with the oxygen to form water. Flue gas made up of carbonmonoxide, carbon dioxide, water and un-reacted oxygen (if any) and othernon-reactive gases are collected from the combustion section andwithdrawn from the regeneration zone as flue gas (20). Thus, the recyclegas and flue gas form a recycle gas loop wherein flue gas is continuallywithdrawn from the process mixed with an oxygen-containing gas toreplenish consumed oxygen and returned to the combustion section asrecycle gas. A small amount of the flue gas is vented (18) off from theprocess to allow the addition of an oxygen-containing gas called make-upgas (16). The oxygen-containing gas is combined with the flue gas toreplace the oxygen consumed by the coke combustion and the combined gasis recycled to the combustion step or section. In the past, theoxygen-containing gas was typically air. The amount of air needed toreplenish the oxygen consumed during the coke combustion is relativelysmall, about 3% of the volumetric rate of the recycle gas streamdepending upon actual inlet oxygen concentration and actual oxygenutilization efficiency.

In a continuous regenerator, all of the oxygen supplied to an upperregion of the bed is consumed, since an abundant amount of coke ispresent. As catalyst particles move downward in the bed and coke isremoved, a point is reached where less than all of the oxygen deliveredis consumed. This is termed the breakthrough point. Typically,breakthrough occurs at a location spaced about half the distance downthe total length of the bed in the combustion section. It is known tothose skilled in the art that catalyst particles of the type used in thehydrocarbon conversion processes of this invention have a large surfacearea, which results from the existence of a multiplicity of pores. Whenthe catalyst particles reach the breakthrough point in the bed, the cokeleft on the surface of the particles is deep within the pores andtherefore the oxidation reaction occurs at a much slower rate.

In a batch regenerator, when the catalyst bed is contacted with recyclegas the coke begins to burn. Generally, the flow rate, temperature, andoxygen concentration of the recycle gas are controlled in order toproduce a combustion front within the catalyst bed and to prevent thetemperature of the combustion front from exceeding about 566° C. (1050°F.). Combusting coke in this manner is well known in the art ofhydrocarbon processing. The combustion front passes slowly from theinlet to outlet of the catalyst bed. The intensity of coke burning andthe rate of progression of the combustion front can be controlled bymonitoring the temperature at various locations within the bed or thebulk temperature of the flue gas stream leaving the bed.

After the combustion step, the regeneration zone will usually includeadditional treatment steps or sections for the catalyst. One such stepis a halogenation step. The halogenation step provides the means ofincorporating and maintaining the desired level of halogen in the finalcatalytic composite. The halogen adjustment step employs a halogen, orhalogen-containing compound in air or an oxygen atmosphere. Thepreferred halogen for incorporation into the catalytic composite ischlorine. The preferred halogen or halogen-containing compound utilizedduring the halogenation step is chlorine, HCl or a precursor of thesecompounds. An oxygen atmosphere is generally employed and desired incarrying out the halogenation step. The presence of oxygen aids in thedispersion of the metallic catalyst components on the carrier. A lowerwater concentration in the environment of the combustion section canfacilitate the halogenation step as catalyst with a lower water contentdrop downward into the halogenation section of the regeneration zone.The concentration of chlorine in the halogenation section is governed bythe Deacon equilibrium equation.4HCl+O₂

2H₂O+2Cl₂

Therefore, to the extent that the catalyst entering the halogenationstep has a lower water concentration it will shift the equation to theright to produce more chlorine for the halogenation step. Since oxygenaids in the re-dispersion of platinum, additional benefits are obtainedwhen the production of the oxygen-deficient make-up gas stream alsoproduces an oxygen-enriched stream that may be passed into thehalogenation step to increase the oxygen concentration and furtherpromote the dispersion of the catalytic metal on the carrier.

After passing from the combustion step to the halogenation step, thecatalyst is usually passed into a drying step or section for the removalof water formed in the combustion step and remaining on the catalystparticles. The typical arrangement for drying the particles charges aheated air stream into the drying step or section of the regenerationzone and contacts the particles in countercurrent flow. Relatively drycatalyst particles are withdrawn (6) from the bottom of the regenerationzone and the water-containing oxygen gas stream (20) flows upward out ofthe drying step.

The water-laden gas stream usually enters the halogenation step orsection to supply the desired oxygen in the combustion section. Gas fromthe drying step and halogen-containing gas mix in the halogenationsection and can either flow upward into the combustion step or sectionor be removed prior to entering the combustion section. Since the gasfrom the halogenation step will usually contain a relatively large waterconcentration, it is desirable to separately withdraw at least part ofthis gas stream before it enters the combustion step or section.

The coke content of catalyst exiting the combustion step isapproximately 0.2% or less of the weight of the catalyst, which isherein defined as complete coke combustion notwithstanding any residualcoke. Much of this residual coke is burned off in the halogenation stepor, if the halogenation step is omitted, in the drying step. Werecatalyst leaving the combustion step to have on it a larger amount ofcoke, the temperature in the step after combustion would rise to anunacceptably high value, as a result of a large heat of combustion.

As noted above, these regions of intense burning are important forcomplete coke removal, but are also difficult to control in a timeefficient manner. Many controller devices are well known in the art inthe area of chemical process control systems or programmable electronicsystems. Here a controller device (22) requires a capability to combinea measured lag time for a temperature wave to travel over a regeneratorzone (26), with an ability to raise inlet temperature (24) using heatingmeans (25) while accounting for a lagging outlet temperature response.Linear temperature ramping or substantially linear ramping, where someshift in slope is permitted as the ramping step begins and/or approachescompletion, provides excellent results. Other ramping functions are alsopossible, including hyperbolic or exponential functions. Initial slopeis generally determined as the ratio of the temperature difference ofthe final target outlet temperature and the initial inlet temperature,to the time period between the time requirement for complete cokecombustion (initially determined by a catalyst with similar coke contentbut without temperature ramping if possible) and the time calculated forstarting the inlet temperature ramping. Note that the final targetoutlet temperature is about equal to the final target inlet temperaturewhen coke combustion has completed.

Future determinations of the time requirement for complete cokecombustion can be iteratively based on prior completed combustion stepsuntil a minimum burn time and heat-up time are obtained with similarcoke content on the spent catalyst. In other words, the time for aninitial effect to reach the outlet can be combined with a final effectto reach the outlet, such that the outlet approximately matches theinlet, and these lag and response times can be subsequently optimized.

Optionally, a controller device (22) will also be able to monitor oxygenconcentration in a recycle gas. Typically, the completion of coke burnis measured with a combination of bed temperature or change in oxygenconcentration. Once satisfactory burn criteria have been met, such as anoutlet bed temperature drop of about 3° C. or more, a proof burn isconducted by increasing the regenerator temperature or the oxygenconcentration. However, the measurement of the parameters outside theregenerator to set criteria for end of burn require scrutiny in order toavoid regenerator outlet temperature dropping below the peak burntemperature or outlet oxygen concentration increasing, which reflectsdropping oxygen utilization. Dropping outlet temperatures requireadditional lag time to wait for increases in inlet temperature tocorrespondingly move down the regenerator. Faster response times can beexpected from increasing oxygen concentration, but a small increase inconcentration can lead to a significant increase in peak burntemperature. Some beds have low flow areas where oxygen in the effluentcan increase, while the low flow area continues to consume all of theavailable oxygen, thus making controlled peak burning difficult over theentire bed by merely controlling inlet and outlet oxygen concentrations.Therefore, it is preferred to control inlet bed and outlet temperatures,generally while maintaining substantially constant oxygen concentrationto avoid uncontrolled peak burning and permanent catalyst damage.

EXAMPLE

The following example is presented only to illustrate certain specificembodiments of the invention, and should not be construed to limit thescope of the invention as set forth in the claims. There are manypossible other variations, as those of ordinary skill in the art willrecognize, within the spirit of the invention.

The lag time can be estimated from the heat up step for regeneratorpreceding the burn step. It takes some time until the changes of inletvapor temperature impacts the temperature at the outlet. A typical heatup curve is shown in FIG. 1 to heat up a regenerator from 149 to 407° C.using an inert gas stream containing at most only insubstantial amountsof oxygen. Here an insubstantial amount of oxygen is an amount less than0.2 vol-%.

FIG. 1 shows a calculation of heat-up temperature waves travelingaxially through a bed of catalyst at one minute intervals. Thisgraphically illustrates the lag time required for a change intemperature at the inlet of the bed, to reach the outlet of the bed.FIG. 1 shows that it may be more than 2 to 3 minutes for this particularbed for an impact to reach the outlet. This lag time is dependant uponrelative gas flow rate, gas heat capacity, solid mass, and solid heatcapacity in the bed, and can be measured from an existing regeneratorzone and used to predict the starting point for inlet temperatureramping. Note that the ultimate time for the outlet to reach the inlettemperature is shown to be about 8 minutes.

Once the bed is heated up to the burn temperature, then the oxygencontaining gas is introduced to begin the burn step. The oxygen contentwas calculated at about 1 vol-% for this bed. FIGS. 2 thru 5 illustratethe importance of proper starting time for temperature ramping whilealso showing the inlet temperature and the increased outlet temperatureassociated with coke combustion. Without any temperature ramping stepthe temperature at the outlet starts to fall in the calculated bed afterabout 91 minutes into the burn step the oxygen efficiency is calculatedto be as low as 70% based on the extra time required to assure completecombustion at a constant inlet temperature such as 407° C.

With an inlet temperature ramping step then the oxygen efficiency iscalculated as high as 96% based on the increased kinetics of burningcoke at a higher temperature such as 482° C. However, if ramping startstoo early, a temperature excursion will occur due to undesirable peakburning as shown in FIG. 2, where a substantially linear ramp up occursat 83 minutes over a period of 18 minutes and the normal peak burntemperature at the end of the combustion is greatly exceeded. FIG. 3shows the axially traveling heat waves at about 9 minute intervals.Thus, oxygen utilization improved but permanent damage has been done tothe catalyst as a result of the temperature excursion, as illustrated inFIG. 2 near 6000 second mark. The temperature ramping step in thisinstance was performed to soon, and even before the outlet temperaturestarted to drop.

In contrast to FIG. 2, FIG. 4 shows a change in start time fortemperature ramping from 83 minutes in FIG. 2 to 89 minutes in FIG. 4and the normal peak burn temperature by the end of combustion is notexceeded in FIG. 4. FIG. 5 shows the axially traveling heat waves atabout 9 minute intervals. Thus, improved oxygen efficiency is combinedwith an improved catalyst life indirectly achieved by avoidingundesirable excursions in peak burn temperature. Here the temperatureramping step was performed closer to when the outlet temperature startedto drop, and thus provided a better adjustment for the lag time for aheat wave to travel through the bed.

Note that in all cases, the oxygen content in the recycle gas duringcombustion was calculated to be substantially constant at approximately1 vol-% oxygen. The term “substantially constant” here refers to normalvariations in measurement and supply not greater than normally expected.Also the temperature ramp was conducted with an 18 minute increase from407 to 482° C., and the outlet temperature eventually reached the inlettemperature once coke combustion has completed, although FIG. 4 does notshow this final point. Convergence of inlet and outlet temperaturessignals completion of coke combustion, and substantially equaltemperatures is defined to be within about a 10° C. range.

1. An apparatus system for effecting the fixed bed regeneration ofcatalyst particles used in the conversion of hydrocarbons, whichcomprises in combination: (a) a reaction zone comprising at least onevessel for contacting a fresh catalyst with a hydrocarbon stream and arecycle hydrogen gas stream to form a coked catalyst; (b) a plurality ofindividual means to the reactor zone for adding and withdrawingcatalyst, hydrocarbons, and recycle hydrogen gas respectively to andfrom the reactor zone; (c) a regeneration zone comprising at least onevessel for combusting the coked catalyst with a recycle oxygen gasstream to form the fresh catalyst; (d) a plurality of individual meansto the regeneration zone for adding and withdrawing catalyst and recycleoxygen gas respectively to and from the regeneration zone; (e) a heatingmeans for raising the temperature of the recycle oxygen gas at an inletto the regeneration zone sufficiently to begin combusting coke from thecatalyst; (f) a device for measuring a lag time for an outlettemperature to respond to and ultimately reach about the same value asan inlet temperature to the regeneration zone; and (g) a controllerdevice for ramping the inlet temperature with the heating means of step(e) using the measured lag time of step (f) in conjunction with ameasurement of a change in the outlet temperature to complete combustingcoke from the catalyst, said controller device optionally capable ofdetecting an outlet oxygen concentration.
 2. The apparatus system ofclaim 1 wherein the catalyst from step (g) is withdrawn through aconduit means from the regeneration zone and added to the reactor zonein a batch or at least semi continuous flow.
 3. The apparatus system ofclaim 1 wherein the heating means of step (e) raises the inlettemperature to a range of about 370° to about 550° C.
 4. The apparatussystem of claim 1 wherein the device of step (f) measures the lag timeduring an initial heating period prior to beginning combustion of coke.5. The apparatus system of claim 1 wherein the controller device of bothsteps (f) and (g) form an integrated controller device.
 6. The apparatussystem of claim 5 wherein the controller device of step (g) uses atemperature change of greater than 3° C. as the change in outlettemperature.
 7. The apparatus system of claim 1 wherein the controllerdevice of step (g) substantially linearly ramps temperature.
 8. Theapparatus system of claim 7 further characterized in that the controllerdevice of step (g) linearly ramps temperature to a maximum of about 600°C.
 9. The apparatus system of claim 1 further characterized in that thereaction zone of step (a) is a catalytic reforming reaction zone. 10.The apparatus system of claim 1 wherein at least part of the means ofstep (d) permits gas to flow axially through the catalyst.